As is well known, in becoming proficient in the game of golf, it is necessary for the golfer to consistently drive the golf ball from the tee box with distance and accuracy. In this regard, once the golfer has obtained proficiency in driving the golf ball (i.e., hitting woods), reduction in the golfer's gross score is achieved due to the resultant reduction in the length and difficulty of the subsequent shot. Although golf swings vary from golfer to golfer, a proper golf swing from the tee box entails that the driver or other wood be swung in an arcuate fashion with the momentum imparted to the golf ball by the club head being controlled by the amount of back swing as well as the impact velocity of the front face of the club head upon the golf ball.
Due to the extremely high impact velocity of the front face of the club head upon the golf ball which typically occurs when the golf ball is driven from the tee box through the use of a driver or other wood, minor variations between the orientation of the front face relative the golf ball upon impact have a significant effect on the trajectory of the golf ball. It is customary in the design of drivers and other woods to form the front face of the club head with horizontal bulge and vertical roll contours which determine the particular spin and trajectory that will be imparted to the golf ball when the same is impacted by the front face of the club head. In this respect, the bulge and roll radii dimensions are tightly controlled to make the golf club more responsive, and allow the golfer to control the rotational direction of the spin and trajectory imparted to the golf ball by selectively varying the orientation of the front face of the club head relative to the golf ball at impact. The bulge and roll radii dimensions are also controlled in certain drivers and woods to make the golf club more forgiving by creating a larger "sweet spot", or correcting for slices and/or hooks by imparting spin onto the golf ball which compensates for an improper orientation of the front face relative to the golf ball at impact.
Over recent years, the use of drivers and woods having metal club heads has become prevalent in the game of golf. These metal club heads have the same overall configuration as the older wooden club heads, but generally define a hollow interior compartment which is foam-filled. The metal club heads are typically produced via an investment casting process wherein a quantity of molten metal material is poured into a mold and about a ceramic coated wax piece disposed therein. Subsequent to the removal of the club head from within the mold, the wax is melted and drained from the club head, thus facilitating the formation of the hollow interior chamber which is defined by the now hollow ceramic shell disposed within the club head. However, due to distortion which occurs during the investment casting process, the front faces of the club heads often do not have precisely the correct bulge and roll radii dimensions. As can be appreciated, such distortion results in the production of a metal club head which does not provide the control or compensation characteristics previously discussed.
In recognition of the deficiencies associated with the production of metal club heads via the investment casting process, there has been developed in the prior art metal club heads for drivers and woods which include an extremely hard insert material disposed within the impact or front face of the club head. Typically, such insert is separately formed and subsequently adhesively bonded or mechanically fastened in a recess formed within the front face. The use of an adhesive has proven deficient, often times resulting in the hardened insert becoming dislodged due to the high impact forces exerted upon the front face of the club head. Additionally, the use of an epoxy adhesive between the hardened insert and the club head often serves to dampen the impact forces and thereby reduce the overall length of the golf shot. In this respect, gluing the pre-fabricated insert into the club head is typically less effective in transferring the load of the golf ball impact to the club head, thus resulting in the loss of feel and distance.
The present invention overcomes the deficiencies associated with prior art metal club heads for drivers and woods by providing a method of manufacturing a metal club head which incorporates a low density, high specific strength front face insert to displace weight away from the center of the club head and increase the golf club's moment of inertia, thus making it a better, more forgiving club to hit. In the present manufacturing method, the insert is consolidated directly into the front face of the club head through the utilization of a dual chamber co-curing assembly. The use of the co-curing assembly is tied to the identification and selection of special resins for the insert which flow and harden at specific points within the insert curing cycle. The present method produces a smooth, attractive outer finish for the insert which is void free. The insert is in direct contact with the metal club head, and in particular the inner surface of a recess formed in the front face thereof. The inner surface of the recess has an arcuate, generally convex configuration which increases the strength of the wall separating the recess from the hollow interior chamber of the club head, allows for the optimal utilization of the insert properties, and maximizes the club head to insert bond strength due to the larger surface area provided thereby.